avformat: set stream sar.den as we set sar.num also

modules/demux/avformat/mux.c

@@ -222,6 +222,7 @@ static int AddStream( sout_mux_t *p_mux, sout_input_t *p_input )
                    &codec->sample_aspect_ratio.den,
                    p_input->p_fmt->video.i_sar_num,
                    p_input->p_fmt->video.i_sar_den, 1 << 30 /* something big */ );
+        stream->sample_aspect_ratio.den = codec->sample_aspect_ratio.den;
         stream->sample_aspect_ratio.num = codec->sample_aspect_ratio.num;
         codec->time_base.den = p_input->p_fmt->video.i_frame_rate;
         codec->time_base.num = p_input->p_fmt->video.i_frame_rate_base;